Telescopic instruments are widely used for magnifying a work area during precision work such as delicate surgery, dental work, inspection of circuit board solder joints, and assembly of miniature parts. A typical telemicroscopic instrument includes a pair of telemicroscopic loupes which are adjustably mounted to an eyeglass frame or headband. The telescopic loupes combine the long working distance of the telescope with the high quality magnification of the microscope. This type of optical instrument provides the user, a surgeon, for example, with a magnified image of the work area with a field of view at about an arm's length.
As one example, the ocular mounting assembly disclosed in U.S. Pat. No. 5,381,263 allows the mounting of a pair of ocular devices to an eyeglass frame, or head mount, and is linearly or rotationally adjustable through five degrees of freedom. An adjustable ocular support assembly with slidably extendable arms provides interpupillary distance, convergence angle and view adjustment of the ocular devices, which are rotatable attached to the support. An adjustable hinge/slide mount assembly is rotatably attached to the ocular support assembly and provides height and view angle adjustment of the ocular devices. When the slidable arms of the ocular support assembly are extended, however, some rotating motion may occur, in particular with heavier oculars and with fully extended support arms. The rotating motion causes vertical misalignment, or divergence, of the axes of the ocular devices. Excessive divergence can cause eyestrain, discomfort and even headaches.
U.S. Pat. No. 6,333,814 improves upon the above design by providing a pair of stabilizers disposed inside the assembly housing and providing stability against rotational motion when the arms are extended. In one embodiment, the stabilizers are interference-fitted balls, retained in position by retainer holes in the assembly housing, and receding into recess cut-outs at the end of the support arms when the arms are fully retracted. In an alternate embodiment, the stabilizers are L-shaped, and can be either an integral part of the housing or bonded to it with adhesive.
Despite these advances, existing designs tend to be physically rather bulky, limiting peripheral vision, for example, when the practitioner looks away from the loupes. FIG. 1 is a drawing that shows front and top views of an older rack assembly, including a housing 20 into which support arms 22 are slidingly engaged to set interpupillary distance using adjusting knob 24. The oculars 14 are attached to the arms 22 through pivots 32 which may be adjustable or fixed in position for a given working distance. A rearward extension 34 having side pins interconnects to a pivot assembly (not shown) which, in turn, may be affixed to eyeglass frames or a headband mount. These features are shown in the issued patents referenced hereinabove. Note that in this older design, the front of the housing 20 is a considerable distance d1 from the front of the oculars, and the height of the side arms 22, h1, is nearly equal to the top of the housing 20, resulting in portions having a relatively large cross-section directly above the eyes of the user. As such, when the user looks away from the oculars 14, these extensions of the support arms tend to get in the way.
FIG. 2 shows a somewhat newer design, wherein the pivot points 32′ are pushed back on the oculars, allowing the distance d2 to be shortened significantly. However, in this case, the cross-sections 22′ of the outwardly extending support arms are nearly the same height as the housing 20′, leading to continual visual obscuration.